Structural influence on the anisotropic intermolecular hydrogen bonding in solid state of substituted thioureas: evidence by X-ray crystal structure

The results of an X-ray crystal structure study of 24 substituted thiourea compounds are reported. Comparison of hydrogen bonding characteristics exhibited by structurally distinct thiourea analogs is especially informative concerning the intermolecular hydrogen bonding that exists in the crystal structure of individual derivatives. In general, all the thiourea derivatives studied showed strong intramolecular hydrogen bonding within their structural framework. In addition, among the thioureas studied, with the exception of the 1-(3-aminopropyl)- imidazole substituted thioureas, all other derivatives formed intermolecular hydrogen bonding with the thiourea sulfur atom and the NH group. However, we discovered for the first time that the presence of the two nitrogen atoms in the heterocyclic ring of 1-(3-aminopropyl)- imidazolyl substituted thioureas formed the hydrogen bond between the imidazolyl N atom and NH group, consequently eliminating the CyS· · ·NH hydrogen bond formation as shown in the packing of the crystal lattice. The following paper describes this novel anisotropy observed in the intermolecular hydrogen bonding among these substituted thiourea derivatives and their salient lattice packing features. q 2003 Elsevier B.V. All rights reserved.